Due to the extreme complexity of the neostriatum's cytoarchitecture only an elementary understanding of this structure's synaptology exists. This is true in regards to the synaptic terminals of both extrinsic and intrinsic origin, and to the relationship of these terminals to specfic neostriatal neurons. For, while it is known which neural structures project to the neostriatum and which striatal neurons have local circuit connections, little is known concerning what types of neurons receive the various synaptic inputs and whether there is a systematic distribution of the synaptic boutons. This proposal is primarily concerned with identifying at the light and electron microscopic level, in the cat, the various types of neostriatal neurons, and than analyzing the distribution of the different synaptic terminals on the dendrites and somata of these cells. Recently a new modification of the Golgi method has been developed (Fairen et. al., 1977) which allows neurons to be silver impregnated and identified at the light microscopic level, and then deimpregnated and studied electron microscopically (EM). Such a technique will be combined with an EM anterograde labeling method (EM-autoradiography). Using this battery of techniques, the different types of neostriatal neurons and the afferent projections to these cells will be studied in the same specimen. The EM-Golgi method will also be used to locate and identify synaptic terminals from local circuit axons and axon collaterals at the ultrastructural level. The information gained from this study should be useful in providing an insight into the basic organization of the adult mammalian neostriatum and establishing an anatomical background for future studies of the neostriatum.